Radial and circumferential magnetic head positioning mechanism

ABSTRACT

Random access information retrieval apparatus for selecting a particular item from a plurality thereof including an improved pair of x-y coordinate digitally positionable devices which are driven by a four-way control valve. A polar coordinate random access information retrieval apparatus including a rotatable recording disc having information recorded on at least one surface thereof, a transducer for detecting said information, radial positioning means for moving said transducer radially along said disc, and angular positioning means coupled to said recording disc for incrementally rotating said disc to position desired information on said disc adjacent said transducer. An improved four-way control valve including a valve housing having a pair of inlet ports for connection to a pressure source and a pair of outlet ports for connection to a load, a first control chamber communicating one of said inlet ports with one of said outlet ports, a second control chamber immediately adjacent said first chamber and communicating the other of said inlet ports with the other of said outlet ports, a diaphragm intermediate said first and second chambers and forming a common wall therebetween, and a diaphragm control means for moving said diaphragm to selectively seal one of said inlet ports in said respective first and second chambers to control the fluid flow between said inlet and outlet ports.

United States Patent Bitzer et al.

Feb. 8, 1972 RADIAL AND CIRCUMFERENTIAL MAGNETIC HEAD POSITIONINGMECHANISM Inventors: Donald L. Bitzer, Urbana; Lyle E. Bandy, Decatur;Roger L. Johnson, Monticello; Dominic 0. Slraperdas, Champaign, all ofI11.

Assignee: University of Illinois Foundation, Urbana,

Ill.

Filed: Aug. 18, 1969 Appl. No.: 850,965

US. Cl. ..340/l74.l C, 251/129, 346/74 MD, 346/137 Int. Cl ..Gl1b 17/02,A63d 15/04, GOld 15/28 Field ofSearch ..340/l74.l C, 174.1 A; 346/74 MD,137; 179/1002 A; 274/4 H, 15 R References Cited UNITED STATES PATENTS3/1963 Stevens .340/1 74. l C 10/1964 Ramrath et ...340/l74.l C 5/1965Robinson ...340/l74.1 C 1/1967 Smith et a1.. ...340/174.1 C 6/ 1969 Freyet a]. ..340/l 74.1 C

PHOTO DETECTOR 0 CONTROL 24 VALVES Pn'mary Examiner-Demard KonickAssistant Examiner-Vincent P. Canney Attorney-Merriam, Marshall, Shapiro& Klose [57] ABSTRACT Random access information retrieval apparatus forselecting a particular item from a plurality thereof including animproved pair of x-y coordinate digitally positionable devices which aredriven by a four-way control valve. A polar coordinate random accessinformation retrieval apparatus including a rotatable recording dischaving infonnation recorded on at least one surface thereof, atransducer for detecting said information, radial positioning means formoving said transducer radially along said disc, and angular positioningmeans coupled to said recording disc for incrementally rotating saiddisc to position desired information on said disc adjacent saidtransducer. An improved four-way control valve including a valve housinghaving a pair of inlet ports for connection to a pressure source and apair of outlet ports for connection to a load, a first control chambercommunicating one of said inlet ports with one of said outlet ports, asecond control chamber immediately adjacent said first chamber andcommunicating the other of said inlet ports with the other of saidoutlet ports, a diaphragm intermediate said first and second chambersand forming a common wall therebetween, and a diaphragm control meansfor moving said diaphragm to selectively seal one of said inlet ports insaid respective first and second chambers to control the fluid flowbetween said inlet and outlet ports.

12 Claims, 10 Drawing Figures V POSITIONING 2 25a LOGIC 26 RADIUS aCONTROL SEGMENT INFO PATENIEurzo elm 3.641.529

SHEET 1 0F 4 PATENTEDFEB B1972 3.641.529

saw u M 4 CONTROL VALVES PHOTO DETECTOR 21% r coumsa CONTROL VALVES,

osmoume RADIUS a SEGMENT INFO CONTROL W Mal. 555222? RADIAL ANDCIRCUMFERENTIAL MAGNETIC HEAD POSITIONING MECHANISM BACKGROUND OF THEINVENTION This invention relates to random access retrieval devices forselecting elements from a plurality thereof and in particular to new andimproved random access apparatus utilizing digitally positionablemembers for selecting the desired elements. Another aspect of thisinvention relates to an improved fourway control valve for controllingthe digital position of such members.

The principles of the present invention are particularly useful inrandom access retrieval systems wherein a single item must be rapidlyselected from a group of such items. For instance, reference may be madeto US. Pat. No. 3,405,457, Versatile Display Teaching System issued toDonald I... Bitzer, wherein there is described a flexiblecomputer-controlled system for transmitting selected information to anumber of student terminals. In such a computer-based education system,thousands of student terminals can be connected to a single computer.Each of these student terminals must be very flexible, providing randomaccess audio or video information, including computer-generated graphicssuperimposed on photographic slide information. However, the cost ofeach terminal must be maintained as low as possible inorder that thesystem advantages in teaching large numbers of students can beeconomically realized.

Various types of random access retrieval systems now exist in the art,however, such devices are extremely cumbersome and expensive. Inparticular, most of said systems utilize pneumatically driven movablemembers selectively operated by relatively large, slow-operating andvery expensive four-way control valves. Pilot valves employing smallsolenoids for controlling the main airflow can somewhat increase theoperating speed of the system, however, known devices of this type stillrequire elaborate construction and are therefore relatively expensiveitems and impractical for use in large numbers.

SUMMARY OF THE INVENTION Therefore, in accordance with the principles ofthe present invention, there is provided an inexpensive, high-speedrandom access retrieval device having two sets of right-angled digitallypositionable pneumatic elements moving rectilinearly in an x-Ycoordinate system for selecting any particular item from a groupthereof. In another aspect of the invention, there is provide a novelfour-way control valve construction containing only a single movablediaphragm and an electrically actuated member controlling an exhaustcontrol port for selectively moving the diaphragm between either one oftwo input ports so as to divert the driving air source to either one oftwo output ports in a valve-switching time of less than onethousandth ofa second and with a switching air loss of less than one-eightieth cubicinch.

In a random access model constructed in accordance with the principlesof the present invention, and adapted for use as a random accessphotographic slide selector, the constructed slide selector was capableof randomly selecting in one-fifth of a second any image from a 4X4-inchfilm plate containing 256 separate images arranged in a 16x16 matrix.The constructed slide selector included eight of the novel four-waycontrol valves of this invention-four each for positioning respective X-and Y-axis piston-cylinder trains.

In another random access model constructed in accordance with theprinciples of the present invention, and adapted for use as a randomaccess audio selector, the audio selector was capable of randomlyselecting any desired audio segment from 2,048 segments, wherein 32segments are recorded in each of 64 radially spaced circular tracks on amagnetic recording disc. The constructed audio selector operated as apolar coordinate selection system having I l of the previously mentionedfour-way control valves-six for positioning a piston-cylinder trainradially to any one of the 64 tracks in about 0.2 second, and five forpositioning another piston-cylinder train to rotate the disc angularlyto any one of the 32 segments in about '15 second.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood from the following detailed description thereof taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates a random access slide selector incorporating theprinciples of the present invention and constructed in accordancetherewith in an improved x-y coordinate selection device utilized, forexample, to select individual slides from a 1 6X1 6 matrix;

FIG. 2 is a perspective view illustrating the x-y digitally positionablepiston-cylinder devices moving rectilinearly along respective orthogonalX- and Y-axis for selecting any one of the 256 slides;

FIG. 3 is a sectional view illustrating the construction details of thedigitally positionable devices shown in FIGS. I and 2;

FIG. 4 is a schematic view illustrating a novel four-way control valvewith the control diaphragm in a first position in accordarice withanother aspect of the present invention;

FIG. 5 is a schematic view illustrating the control valve of FIG. 4 withthe diaphragm in a second operating position;

FIGS. 6 and 7 are schematic views illustrating the construction detailsof the novel four-way control valve in accordance with this aspect ofthe invention;

FIG. 8 is a diagrammatic view of a random access audio selector inanother aspect of this invention illustrating a novel polar selectiondevice;

FIG. 9 is a partial elevational view illustrating incremental rotationof the recording disc and radial positioning of the reading and/orplayback head during the selection procedure; and

FIG. 10 is a partial plan view illustrating the construction details ofthe hub key slidably engaged in the spiral-slotted shaft forincrementally rotating the recording disc with respect to theconstant-speed turntable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1-3there is illustrated a random access slide selector 10 includingdigitally addressable, pneumatically driven piston-cylinders 12 fordriving a film plate 14 in a first direction, and a similar set ofpneumatically driven elements 16 arranged perpendicular to the elements12 for corresponding movement of the slide tray. The film plate 14contains a square matrix of 16x16 or 256 images thereon and is mountedwithin a slide tray 18 which is slidably mounted on parallel rods 20,22. The slide tray or carriage 18 including the rods 20, 22 are slidablymounted by suitable means 24, 26 to a second pair of stationary rods 28,30. As indicated most clearly in FIG. 2, piston-cylinders 12 control theposition of the slide tray 18 along the parallel rods 20, 22, and thewhole assembly is slidably positioned along parallel rods 28, 30 undercontrol of the piston-cylinders 16. Suitable bracket means 32 areprovided for rigidly mounting the slide selector components to a base34.

The piston-cylinders trains I2, 16 are of a construction well known inthe art in which either side of the cylinder is pressurized while theother is vented to the atmosphere. A seriesmounted set of fourpiston-cylinders 12 are shown in FIG. 3, in which piston-cylinders 12aand are fully extended whereas cylinders 12b and 12d are fullyretracted. The load 36 representing the slide tray 18 is connected tothe free end of the last piston 38. Each of the remaining pistons has afree piston end 40 slidable movable between two end positions of acylinder, and a captured piston end 42 which is mounted to the nextsucceeding cylinder. Either one of the piston cylinder inlet ports 44,46 is pressurized while the other is vented to the atmosphere in orderto selectively move the respective piston end 40 between the twocylinder end positions. The cylinder nearest the fixed end must displaceall of the other seriesmounted cylinders plus the load; therefore, thecylinder 12a with the smallest stroke length is placed at the fixed end.Cylinders 12b, 12c and 12d with increasing stroke length are placed inseries from the fixed end to the load end. For example, referring toFIGS. 1 and 2, within piston-cylinder group 12, end 48 is fixed inposition with respect to parallel rods 20, 22 whereas end 50 is slidablemovable along the rods. Similarly, in piston-cylinder group 16, end 52is fixed in position with respect to parallel rods 28, 30 whereas end 54is slidably movable along the rods.

As is shown in FIG. 3, the piston-cylinders are each constructed withthe succeeding cylinders having twice the stroke length of the precedingcylinder. Thus, cylinder 12a has a stroke length L, cylinder 12b astroke length 2L, cylinder 12c a stroke length 4L, and cylinder 12d astroke length 8L. The stroke length of the smallest cylinder is chosenso as to correspond to the smallest incremental displacement requiredalong rods 20, 22 and 28, 30.

As an example, in a constructed model of the invention, the film plate14 is 4 inches square and contains 256 images arranged in a I6 16matrix. Thus, each image is AX'A inch so that the stroke length of thesmallest cylinder 12a is Mr inch, cylinder l2b% inch, cylinder l2c-linch, and cylinder l2d2 inches. As an example of digital addressing ofthe piston cylinder trains 12, 16, initially, the movement ofpistoncylinders 16 along rod 28 can be defined as along the X-axis,whereas movement of piston cylinder 12 along rod 22 can be defined asalong the Y-axis of an orthogonal x-y coordinate system. If the image atF11 and y==4 is to be selected, the 2- inch, /z-inch, and 84-inch pistoncylinders of group 16 are to be selected on the X-axis (1011 in binarynotation) and the 1- inch piston cylinder of group 12 on the Y-axis(0100) are activated. This would place image 140 directly above lightsource means 60 for projecting the image through lens assembly 62 tosuitable means, such as reflector 64, and on to screen means 66. It isunderstood that the projection means illustrated in FIG. 2 have merelybeen given for purposes of an example. Thus, in the display teachingsystem previously mentioned, a random access slide selector 10 would belocated at each student terminal, and the selected image 14a would beprojected for display at the particular station display means.

The schematic views of FIGS. 4 and 5, and the sectional valve assemblyviews of FIGS. 6 and 7 illustrate a unique fourway control valve foractivating the piston-cylinders l2 and 16. It is to be understood thatwhile the four-way control valve to be illustrated hereinafter can beapplied to any apparatus wherein it is desired to selectively connecteither of two output ports with a fluid source, it is particularlyuseful for driving digitally positionable devices. Furthermore,particularly in view of the ease of construction and corresponding lowcosts thereof, the control valve illustrated in FIGS. 4-7 when utilizedin the random access aspect of this invention provides significantlyimproved apparatus which can be practically employed in a displayteaching system as previously described.

In particular, with reference to FIG. 1, there is illustrated a firstcontrol valve assembly 72 containing a series of four control valves 74with suitable outlet ports 76, 78 for connection to respectivepiston-cylinder inlet ports 44, 46 (FIG. 3). A similar assembly 82 ofcontrol valves 74 are provided with corresponding outputs 76, 78connected to respective input ports of piston-cylinder group 16. It mustbe noted from FIG. 1, that each of the four-way control valves of thepresent invention are identical, and are extremely compact so that anassembly of four such control valves can readily be provided.

Reference may be had to FIGS. 4 and wherein the basic operatingcomponents of the unique four-way control valve of this aspect of theinvention are illustrated in schematic form. Inlet port 1 UPI) connectsan air source from port 84 through passageway 86 and terminates in aridge portion 88 projecting from a top wall 90 of control chamber 92.Outlet passageway 94 communicates with chamber 92 at rear chamber wall90 and ends in outlet port 1 (O?!) for connection to input port 44 of arespective piston-cylinder in group 12 or 16. A passageway 96intermediate outlet port 1 and control chamber 92 communicates withpassageway 94 and ends in an exhaust control port 1 (ECPl). Abidirectional solenoid plunger 98 having resilient stopper valves I00and 102 on opposite ends thereof is provided for selectively sealing orunsealing the exhaust control ports. Well-known electrically actuatedcoil means, shown schematically at 103, selectively operates thesolenoid plunger 98 for movement in the respective directions toselectively seal the exhaust control ports.

A diaphragm 104 forms a common wall between control chamber 92 andcontrol chamber 106. Passageway 108 communicates the air source input atport 84 with inlet port 2 (IP2) having an opening within chamber 106 atthe top of ridge 110 projecting above bottom wall 112 of the chamber.Passageway 1 14 interconnects chamber 106 with outlet port 2 (0P2) forselectively directing the fluid flow to pistoncylinder inlet port 46. Abranch line 116 intermediate chamber 106 and outlet port 2 extends frompassageway 114 and ends in exhaust control port 2 (ECPZ). Exhaustcontrol 1 is closed thereby enabling airflow from input 84 to flowthrough passageway 86 and inlet port 1 into chamber 92, throughpassageway 94, and outlet port 1 so as to move the piston away frominput port 44 to the position shown in FIG. 4. Note that there is nostatic air loss in the control valve, since although passageway 116 isopen, inlet port 2 is sealed by diaphragm 104. Since the area ofdiaphragm 104 is substantially greater than the ridge opening in chamber106 at inlet port 2, the differential force is greater in controlchamber 92 and the diaphragm 104 is urged against ridge 110 therebyshutting ofi inlet port 2.

When the solenoid plunger 98 is reversed as illustrated in FIG. 5 so asto seal exhaust control port 2, the minute dynamic leak through exhaustcontrol port 1 lowers the pressure in control chamber 92 below that incontrol chamber 105. Diaphragm 104 therefore reverses its position andrapidly shuts off inlet port 1 in chamber 92. Thus, in the position ofthe control valve illustrated in FIG. 5, outlet port 2 is connected viapassageway 114, control chamber 106, and inlet port 2 to the air supplyso as to urge piston 120 away from the piston-cylinder input port 46. Itmust be noted that in this case, the differential force on diaphragm 104is greater in control chamber 106 than in chamber 92, and there issimilarly no static air leak through outlet port 1 or exhaust controlport 1 since control chamber 92 is sealed by diaphragm 104 from the airsource.

Referring now to FIGS. 6 and 7, there is illustrated in detail afour-way control valve 74 constructed in accordance with the principlesof this aspect of the invention. In particular each valve assembly 74 isformed of two identical molded-plastic half-sections 122, 124, eachhaving a ridge 88 extending from a cavity 92 in one face 126 of therespective valve half-section. Passageway 86 is then formed by drillingthrough ridge 88 a selected distance within the valve half-sectionperpendicular to the face 126, and thereafter drilling at anintersecting point through surface 128 of the half-section untilcommunication is made with the first passageway as illustrated in FIG.7. Similar drilling procedures are used to form passageway 94 bydrilling through surface 130 (see FIG. 6) and through cavity wall 90until an output port 1 is formed which connects through passageway 94with the cavity 92. A hollow metal insert 132 or other suitable meanscan be provided to form the output port 1. Exhaust control port 1 andconnecting passageway 96 is formed by drilling through surface 134 toconnect with passageway 94 and inserting a hollow metal member 136.

The valve half-section 124 is constructed in a manner similar to that asdescribed above in connection with half-section 122. Thereafter, a verythin cavity can be made in the face 126 of half-section 122 or the face138 of half-section 124 so as to receive a thin rubber diaphragm 104extending across either cavity 92 or 106 and cemented to correspondingfaces 126 or 138. The half-sections 122 and 124 are thereafter assembledwith faces 126 and 138 in contact to form interface 140. Thehalf-sections are held together by suitable mounting means such asbolt-and-nut means 142.

As is shown in FIG. 6, in the assembled configuration, the diaphragm 140forms a common wall between control chamber or cavity 92 and controlchamber or cavity 106. The electrically actuated coil means 103 issuitably mounted to the control valve assembly.

Thus in accordance with this aspect of the invention, there has beenprovided a very readily constructed, efficient, economical, andfast-operating control valve which is especially adaptable to therectilinear-type x-y slide selector mechanism previously described, andwhich is also utilized in a novel polar coordinate selection system forretrieving audio information as will be more particularly describedhereinafter. As an example of the present invention, a model constructedin accordance therewith operated with -12 lb. per sq. inch pressure witha valve switching time of less than one-hundredth of a second. Thedynamic air loss during switching was less than one-cightieth cubicinch.

Instead of the rectilinear-type orthogonal coordinate selection systemshown in FIGS. 1 and 2, similar devices can be provided for selectingany one of a plurality of items in a polar coordinate random accesssystem. A polar coordinate random access system is especially useful forselecting desired audio information stored on standard magnetic discsrotating with respect to a magnetic transducer. In such a system, theangular and radial position of the transducer is varied to selectinformation. The angular position can be obtained by mounting thetransducer on a suitable bracket means connected to the central shaft ofa magnetic disc drive mechanism. If the central shaft is provided with apinion gear, a digitally positionable rack gear driving the pinion canbe provided for rotating the shaft through 360 and thereby positioningthe transducer in any desired angular increment. The radial position ofthe transducer along a particular radius extending from the shaft andradially along the disc can be provided by a second digitallypositionable piston-cylinder combination.

A preferred alternative polar coordinate system 200 is illustrated inFIGS. 8, 9 and 10, wherein there is shown a random access system inwhich information is recorded on and played back from a flat magneticdisc. The recording medium is a standard magnetic recording disc 202having an oxide coating on at least the top surface thereof forrecording information. The disc is mounted to a hub 204 for rotationtherewith by suitable means such as a key 206 in flange 208 overlyingthe disc 202. The disc 202 is normally positioned on and rotates with ahigh moment of inertia turntable 210 for access by a levitating magneticread (playback) and/or write head 212 mounted immediately above the disc202. As will be described in more detail hereinafter, the disc 202 isincrementally rotated with respect to the turntable 210 during theangular selection procedure. It is to be understood that for conveniencein illustration, only a partial segment of the disc 202 and turntable210 are illustrated in FIG. 8, and similarly, the disc is shown asseparated from the turntable, whereas it is normally located directlythereon.

Magnetic head 212 is mounted for incremental rectilinear movementradially on disc 202 towards hub 204 by means of a first set ofpneumatically driven elements 214 constructed similar to thepneumatically driven elements 12 and 16 previously described. As shownin FIG. 8, the smallest pistoncylinder has one end 215 rigidlymaintained in position by fixed means 216 and the opposite end 217 ofthe largest piston-cylinder element attached to magnetic head 212. Acorresponding set of four-way control valves 218 each constructedsimilar to the previously described control valves 74 of FIGS. 4-7 isprovided for controlling the incremental rectilinear displacement of themagnetic head 212 radially along disc 202.

Around the rim 220 of turntable 210 there is placed a series of markers222 for detection of photodetector means 224 so as to detect the angularposition of disc 202 during rotation with respect to a referenceposition. A reference marker 226 is provided on rim 220 to indicateangular displacement of the disc from the reference position. Instead ofthe optically sensed markers 222, other marking means, such as amagnetically coded strip around rim 220 with a corresponding sensinghead can be utilized. It is to be understood that the turntable 210 isrotated by any convenient rotating means (not shown), preferably at aconstant rotational speed.

Positioning of the disc 202 in angular direction with respect to thehigh-mass turntable 210 during the information selection procedure isprovided by a vertically movable shaft 230 passing through a centralaperture in the turntable and having a spiral slot 232 extending alongthe length thereof to accommodate the key 206 in hub 204. Key 206extends radially through hub 204 and into the spiral slot 232 as shownmore clearly in FIG. 10. The hub 204 and attached recording disc 202 arefree to rotate with respect to turntable 210 in response to verticalmovement of the shaft 230. The shaft 230 is moved in incremental stepsby means of a vertical arm 234 having a ball bearing 236 mounted at oneend thereof and a toothed gear segment 238 at the other end thereof forengagement with a rotating gear member 240. The rotating gear member 240is driven by a horizontal arm 242 having a toothed gear section 244engaging the gear member 240 and being moved incrementally in horizontalposition by means of a second set of pneumatically driven elements 246under control of suitable control valves 248 in an arrangement similarto the pneumatic elements 214 and control valves 218 provided forradially positioning the magnetic head 212. One end 249 of pneumaticdriven elements 246 is fixed by suitable rigid means 250 while the otherend 251 is connected to the horizontal arm 242. Thus, operation of oneof the pneumatic driven elements 246 moves shaft 230 vertically toenable the key 206 to slide along spiral slot 232 and thereby rotateattached disc 202 through a corresponding incremental angulardisplacement from its initial position. During nonoperation of thepneumatic elements 246 the disc 202 rotates simultaneously and at thesame rotational velocity as the turntable 210. It is to be understoodthat during rotation of the disc from one angular position to another,the magnetic head 212 is inactivated so that no information istransferred to or from the disc 202 during the selection interval. Theselection interval is, of course, much less than the reading intervalduring which information is being played back from the disc 202.

Photodetector 224 senses the markers 222 and the corresponding referencemarker 226 so as to indicate through signals provided by counter 252 theangular position of turntable 210, which information is coupled into apositioning logic control apparatus 254 on input line 256. Positionalinformation corresponding to the desired information recorded on disc202 and containing a corresponding radius and segment address is alsocoupled on input line 258 to the positioning logic control apparatus254. Positioning logic control apparatus 254 integrates the signals fromthe input lines to provide suitable control signals on output lines 260and 262 to the respective control valves 218, 248 for radiallypositioning magnetic head 212 and angularly positioning the magneticdisc 202.

In the preferred embodiment of this aspect of the invention, the polarcoordinate random aspect of the invention, the polar coordinate randomaccess system 200 illustrated in FIGS. 8-l0 is utilized as a source ofaudio information in a display teaching system of the type shown in thepreviously mentioned US Pat. No. 3,405,457, Versatile Display TeachingSystem," Donald L. Bitzer, issued Oct. 15, 1968. As indicated, thispatent discloses a flexible computer-controlled display system fordisplaying various instructional material to a group of studentstations. The present random access system 200 is especially desirableas a source of audio infonnation which has previously been recorded onany one of 64 circular tracks each located at a discrete radial distancefrom the hub 204, and indicated for illustration by the referencenumeral 264 in FIG. 8. Each track 264 contains 32 recording segments,with the angular distance between each segment corresponding to thedistance between markers 222 on the turntable rim 220. The turntable 210is rotated at a speed of approximately 10 seconds per revolution.

In an actual model constructed in accordance with this aspect of theinvention, the piston-cylinder set 214 comprised a six-unit pneumaticpiston-cylinder train with the size and movement of the smallest radialpiston corresponding to the radial distance between recording tracks ondisc 202, or as commonly termed, the intertrack distance. Thus, thereading head 212 could be incrementally positioned to any one of the 64tracks by selectively operating combinations of one or more of the sixpiston-cylinders. The pneumatic set 246 comprised a five-unit pneumaticpiston-cylinder train capable of angularly incrementally rotating thedisc 202 through any one of 32 steps. In this case, the size andmovement of the smallest piston connected to horizontal arm 242corresponded to the distance between segments on each track. Thus, withthe piston-cylinder set 214 in the fully retracted position, magnetichead 212 is in communication with the outermost track on disc 202, andwhen fully extended, the magnetic head 212 is in communication with theinnermost track, with each of the 64 tracks being capable of selectionthrough control signals from positioning logic control apparatus 254coupled through the control valves 218.

Since the piston-cylinder set 214 is fixed at one end, and the magnetichead 212 is selectively moved in relation thereto, the radiusinformation on line 258 corresponds to the actual address of the desiredinformation on disc 202. However, since the turntable 210 is rotating ata constant speed, its present position will be sensed by photodetector224 and this information coupled on input line 256 to the positioninglogic control unit 254, so that the present position information can becombined with the address of the desired position as applied on inputline 258. Positioning logic control unit 254 is therefore a standardintegrating circuit which in effect subtracts the address of the desiredsegment position on input line 258 from the detected present positioninformation on input line 256 to provide suitable signals on output line260 coupled to control valves 248.

in the random access apparatus constructed in accordance with thisaspect of the invention, shaft 230 is moved vertically a maximum ofapproximately 3 inches in rotating the disc 202 through a maximumrotational angle of 360in other words, through each of the 32 segmentson a single track. The spiral slot 232 on shaft 230 has a low pitch soas to facilitate the ease of angularly rotating disc 202 in response tovertical movement of the shaft 230.

FlG. 9 illustrates a schematic view for illustrative purposes of aselecting sequence wherein the shaft 230 is displaced vertically anincremental amount which has incrementally rotated the disc 202 withrespect to turntable 210 until the desired segment position is locatedbeneath the head 212. During rotation of the disc 202, the head 212 hasalso been moved radially on the disc to one of the desired 64 tracks. Amechanism such as a weighted cap can be placed over the hub 204. Thisurges the key 206 to slide along spiral slot 232, thereby minimizingvertical movement of the disc and enabling the disc to rotate withrespect to the turntable during vertical movement of shaft 230 in thesegment selection procedure.

Various alternative arrangements of the inventions herein can'beprovided. For instance, instead of the single spiral slot 232 and key206, a shaft with two or four parallel spiral grooves or slots withassociated keys could be provided to distribute the forces more evenly.In another alternative embodiment, a return spring having one endmounted in the bottom end of shaft 230 and the other end fixedly mountedin position, and cooperating with a wire attached at one end to theshaft bottom and at the other end to the piston-cylinder ele ments 246can be utilized in place of the arms 234, 242 with toothed gear segments238, 244 and rotating gear member 240 shown in FIG. 8. In operation, thewire is moved longitudinally by the associated piston-cylinder elementsto vertically move shaft 230, and the return spring is utilized toreposition the shaft.

Therefore, the foregoing detailed description has been given forcleamess of understanding only, and no unnecessary limitations should beunderstood therefrom, as modifications will be obvious to those skilledin the art.

What is claimed is:

l. Random access information retrieval apparatus for retrievinginformation from a rotatable recording disc having information recordedin information segments on at least one surface thereof, said apparatuscomprising:

a transducer for detecting said information on said recording disc;

radial positioning means for moving said transducer radially along saidrecording disc;

a turntable for supportingly transporting said recording disc duringrotation;

means for rotating said turntable at a constant rotational speed; and

incremental angular positioning means including angular selection meansfor incrementally rotating said recording disc with respect to saidturntable to angularly position desired information segments on saiddisc with respect to said transducer;

said incremental angular positioning means and said radial positioningmeans cooperating to position said disc adjacent said transducer fortransferring information from said disc.

2. Random access information retrieval apparatus according to claim 1,including a hub mountable to said recording disc, said hub includingmeans for positionally engaging said incremental angular positioningmeans for operation thereby.

3. Random access information retrieval apparatus according to claim 1,wherein said angular selection means comprises vertical positioningmeans including a vertical shaft having a spiral slot slidably engagingsaid disc for rotating said disc as said shaft is moved vertically, anddigitally positionable drive means coupled to said vertical shaft forincrementally moving said shaft.

4. Random access information retrieval apparatus according to claim 1,wherein said radial positioning means includes radial selection meansand digitally positionable members connected intermediate said radialselection means and said transducer for moving said transducer inincremental steps radially along said disc.

5. Random access information retrieval apparatus according to claim 1,wherein said radial positioning means includes means for incrementallymoving said transducer radially along said disc simultaneously withrotation of said disc in selective incremental steps relative to saidturntable.

6. Random access information retrieval apparatus according to claim 5,wherein said angular selection means includes control signal means, anddigitally positionable members coupled to said disc, said membersextending and retracting in response to said control signal means torotate said disc in said selective incremental steps.

7. Random access information retrieval apparatus according to claim 6,including detector means for detecting and indicating the instantaneousposition of said disc during rotation by said turntable.

8. Random access information retrieval apparatus according to claim 7,wherein said detector means includes reference markers associated withinformation segments on said turntable and a sensor responding to saidreference markers for indicating the position of said disc.

9. Random access information retrieval apparatus according to claim 8,wherein said reference markers comprise optical designations on the rimof said turntable, and said sensor comprises photodetector meansresponse to said optical designations.

10. In random access information apparatus for recording on andretrieving information from a rotatable member having a plurality ofinformation segments on at least one surface thereof, including aturntable for supporting said recording member, means for rotating saidturntable at constant rotational speed, a magnetic transducer radiallyoperational along said recording member surface for recording andplaying back said information on said recording member, the improvementcomprising:

incremental angular positioning means for incrementally rotating saidrecording member with respect to said turntable to angularly positionthe desired information segment with respect to said transducer; and

radial positioning means for moving said transducer radially along saidrecording member;

said incremental angular positioning means and said radially positioningmeans cooperating to position said recording member adjacent saidtransducer for transferring information to or from said member. 11.Random access information apparatus according to claim 10, wherein saidradial positioning means and said incre- 22 3 33 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent No. 3 Dat d February 8 1972lnventor'(s) Donald Bitzer Lyle E. Bandy, Roger L. Johnson,

and UOIIllI'llCT U. DKSTPGIOQS It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

I V I 1 Column 1, line 47, "provide" should be provided. Column 1, line54, "thousandth" should be -hundredth-.

Column 2, line 30, after "polar" add "coordinate".

Column 2, line 38, after "constant" take out Column 3, line 6,."slidable" should be --slidably.

Column 6, line 2 "of" (second. occurrence) v should be -by-- Column 6,line 65 and 66, "aspect of the invention, the polar. coordinate random"should be deleted.

Signed and sealed this 8th day of August 197' (SEAT) Attest:

EDWARD I'I.FI,ETCHER,JR. RUEERT GOTTSC-IIALK $4 I V Awesoing, OfficerCommissioner of Patents P0405) UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent Nor 3 Dated ry 8 197.2

Inventor) Donald L. Bitzer, Lyle E. Bandy, Roger L. Johnson,

and uominifu. bkaperdas It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 47, "provide" should be --provided--. Column 1, line 54,"thousandth" should be "hundredth".

Column 2, line 30, after "polar" add "coordinate".

Column 2, line 38, after "constant" take out 6 Column 3, line 6,"slidable" should be slidably--.

Column 6, line 2,, "of" second occurrencefshould be by-- W a Column 6,line 65 and 66, "aspect of the invention, the polar. coordinate random"should be deleted.

Signed and sealed this" 8th day of August 197? Attest:

EDWARD M.FLETC ER ,JR{ ROBERT GUTTSCf-HALK Attesting OfficerCommissioner of Patents

1. Random access information retrieval apparatus for retrievinginformation from a rotatable recording disc having information recordedin information segments on at least one surface thereof, said apparatuscomprising: a transducer for detecting said information on saidrecording disc; radial positioning means for moving said transducerradially along said recording disc; a turntable for supportinglytransporting said recording disc during rotation; means for rotatingsaid turntable at a constant rotational speed; and incremental angularpositioning means including angular selection means for incrementallyrotating said recording disc with respect to said turntable to angularlyposition desired information segments on said disc with respect to saidtransducer; said incremental angular positioning means and said radialpositioning means cooperating to position said disc adjacent saidtransducer for transferring information from said disc.
 2. Random accessinformation retrieval apparatus according to claim 1, including a hubmountable to said recording disc, said hub including means forpositionally engaging said incremental angular positioning means foroperation thereby.
 3. Random access information retrieval apparatusaccording to claim 1, wherein said angular selection means comprisesvertical positioning means including a vertical shaft having a spiralslot slidably engaging said disc for rotating said disc as said shaft ismoved vertically, and digitally positionable drive means coupled to saidvertical shaft for incrementally moving said shaft.
 4. Random accessinformation retrieval apparatus according to claim 1, wherein saidradial positioning means includes radial selection means and digitallypositionable members connected intermediate said radial selection meansand said transducer for moving said transducer in incremental stepsradially along said disc.
 5. Random access information retrievalapparatus according to claim 1, wherein said radial positioning meansincludes means for incrementally moving said transducer radially alongsaid disc simultaneously with rotation of said disc in selectiveincremental steps relative to said turntable.
 6. Random accessinformation retrieval apparatus according to claim 5, wherein saidangular selection means includes control signal means, and digitallypositionable members coupled to said disc, said members extending andretracting in response to said control signal means to rotate said discin said selective incremental steps.
 7. Random access informationretrieval apparatus according to claim 6, including detector means fordetecting and indicating the instantaneous position of said disc duringrotation by said turntable.
 8. Random access information retrievalapparatus according to claim 7, wherein said detector means includesreference markers associated with information segments on said turntableand a sensor responding to said reference markers for indicating theposition of said disc.
 9. Random access information retrieval apparatusaccording to claim 8, wherein said reference markers comprise opticaldesignations on the rim of said turntable, and said sensor comprisesphotodetector means response to said optical dEsignations.
 10. In randomaccess information apparatus for recording on and retrieving informationfrom a rotatable member having a plurality of information segments on atleast one surface thereof, including a turntable for supporting saidrecording member, means for rotating said turntable at constantrotational speed, a magnetic transducer radially operational along saidrecording member surface for recording and playing back said informationon said recording member, the improvement comprising: incrementalangular positioning means for incrementally rotating said recordingmember with respect to said turntable to angularly position the desiredinformation segment with respect to said transducer; and radialpositioning means for moving said transducer radially along saidrecording member; said incremental angular positioning means and saidradially positioning means cooperating to position said recording memberadjacent said transducer for transferring information to or from saidmember.
 11. Random access information apparatus according to claim 10,wherein said radial positioning means and said incremental angularpositioning means, respectively includes incremental drive means forradially positioning the transducer and angularly positioning therecording member in incremental steps.
 12. Random access informationapparatus according to claim 11, wherein said incremental drive meansincludes a pair of digitally positionable members operable inincremental steps each respectively coupled to said magnetic recordingmember and said magnetic transducer, and selection signal means foroperating said digitally positionable members in selected incrementalsteps to position the desired information segment adjacent saidtransducer.